The present invention relates to a sensing device for sensing the geometry of an object, like a wheel, particularly a vehicle wheel, and for determining geometrical dimensions of the object, a service apparatus for a wheel, which is equipped with a sensing device, for determining geometrical dimensions of a wheel and a method for determining geometrical dimensions of a wheel, like a vehicle wheel, for determining geometrical dimensions of the wheel.
In practice, wheel service machines are known, like a mounting/demounting machine for mounting a tyre to a rim of a wheel or for demounting a tyre from a rim of a wheel, in particular a vehicle wheel, or a wheel balancer on which a wheel, or only the rim or the tyre of a tyre/rim combination, is inspected, e.g. for detecting unbalances in the wheel or deformations of the tyre or the rim, the rim profile or the characteristics of the tyre.
From EP patent application 2 360 461, an apparatus for determining geometrical dimensions of a wheel is known, which includes a measuring unit with a sensing device, like an ultrasonic sensing device, including an emitter/receiver transmitter for scanning the wheel, an angle measuring means including accelerometer means to measure a pivot angle. The measuring unit is mounted to a hood of a wheel balancer, and is pivoted together with the hood for executing a measurement operation.
In DE patent application 100 35 118, a scanning device is disclosed, which is part of a wheel balancer. The scanning device is used for scanning the rim profile of a wheel to be balanced, and for identifying the position in which a balancing weight is to be attached to the rim. A light source and a receiver are separately mounted on respective carrier plates which are pivoted by a stepper motor. The angular position of the light source and the receiver is detected by a rotary encoder.
In these known devices, the pivotal movement of the sensing device during the measuring operation is executed manually or by a stepper motor which has a fixed increment or pitch. Thus, the actual position of the sensing device and the resolution of the scan is restricted, dependent on the pitch or step size of the stepper motor. In order to increase e.g. the solution of a scan, namely the number of points on a predefined length or area, the stepper motor may be equipped with a reduction gear. Moreover, the known devices are of a complex construction and sensitive to impurities, which influences the accuracy of the measurement or positioning results. Additionally, the components of the sensing device have to be aligned to each other after assembling which is time consuming.
Thus, it is an object of the present invention to provide a sensing device, a wheel service apparatus and a method for determining geometrical dimensions of a wheel, which overcome the above mentioned drawbacks, and which enable a simplified construction and an efficient control of the measurement operation.